1. Field of the Invention
The present invention relates to a tire sensor device which collects and processes information from sensors mounted in a tire and transmits the processed information to the car body side and to a tire information transmission method.
2. Description of the Prior Art
Heretofore, there has been implemented a tire air pressure monitoring device which detects the inside pressure of a tire by mounting a pressure sensor device for detecting the pressure of a gas filled in the tire on a surface facing a tire cavity area of a wheel and transmits the detected information to the car body side so as to inform a driver of the inside pressure of the tire. FIG. 8(a) is a block diagram showing the constitution of a tire pressure sensor tag 80 which is the pressure sensor device of the prior art. This tire pressure sensor tag 80 comprises an air pressure sensor 81 for detecting the inside pressure of the tire, an analog amplifier 82 for amplifying a tire inside pressure signal detected by the air pressure sensor 81, a processing circuit 83 for processing a pressure signal indicative of the inside pressure of the tire based on a signal from the above analog amplifier 82, a transmitter 85 for modifying a carrier based on a pressure signal detected by the above air pressure sensor 81 and processed by the processing circuit 83 and transmitting the modified carrier to the unshown car body side from an antenna 84, and a battery 86 for supplying power for driving these devices. The above air pressure sensor 81 is composed of a diaphragm made of an elastic material such as silicon rubber, mounted on a substrate 87 as shown in FIG. 8(b), and the above analog amplifier 82, processing circuit 83, transmitter 83 and antenna 84 are also formed on the above substrate 87. The battery 86 such as a button type battery is mounted on the substrate 87 separately from the above constituent elements (refer to patent document 1, for example).
However, as the above battery drive type tire pressure sensor tag 80 comprises the transmitter 85 for transmitting the above tire pressure information to the car body side in addition to the analog amplifier 82 and the processing circuit 83, the service life of the battery is short and therefore the above tire pressure sensor tag 80 must be exchanged regularly.
Meanwhile, as shown in FIG. 9, there is known a tire sensor device 90 which comprises an RF transponder for responding to a carrier signal (query signal) from a call unit 90F in the tire 1 to collect data on the inside pressure of the tire. Since this tire sensor device 90 comprises an interface circuit 93 for rectifying a received RF signal and supplying power to other circuits such as a clock circuit 91 as a signal processing circuit, a sequencer circuit 92 and an unshown drive circuit and uses the above RF signal which is a query signal as an electric energy source for transmitting a digital signal regarding tire pressure data measured by an on-chip pressure sensor 90P, it does not require a battery and can detect the inside pressure of the tire stably for a long time. In the above tire sensor device 90, an on-board oscillator (not shown) installed in a transmission circuit 94 operates to transmit data on the inside pressure of the tire measured by the on-chip pressure sensor 90P to the car body side from an antenna 95 only when it receives the query signal (refer to patent document 2, for example).
Meanwhile, to enhance the running stability of an automobile, it is desired that the conditions of the running tire should be estimated accurately and fed back to car control. It is considered that this information makes possible the advanced control of an ABS brake and a car attitude control device making use of the ABS brake to further enhance safety.
As shown in FIGS. 10(a) and 10(b), there is proposed a tire sensor device 100 which comprises sensors such as a pressure sensor 103, a temperature sensor 104 and a revolution sensor 105 all of which are installed in the tire and mounted on the substrate 102 of a housing 101, a driver 106 for driving these sensors and an on-board power source 107 to collect a plurality of tire data and transmit them to the car body side. When this tire sensor device 100 receives a query signal from a remote interrogator 100F installed on the car body side, it activates the sensors 103 to 105 to detect tire data such as tire pressure and tire temperature, digitizes the detected tire data, transmits these data to the central processing device 108a of a transponder 108 installed in the housing 101 to process them, and transmits the processed data to a car control device 100S on the car body side from an antenna 109. Thereby, various tire data can be obtained with the single tire sensor device 100 (refer to patent document 3, for example).    Patent document 1: JP-A 2003-347811    Patent document 2: JP-B 2002-511355    Patent document 3: JP-B 11-504585